Method of near-net-shape forged molding of coupler knuckle of railway vehicle

ABSTRACT

The present invention provides a method of near-net-shape forged molding of the coupler knuckle of the railway vehicle. The present invention solves the problems that the manufacturing the forged coupler knuckle is difficult, and the process is complex, etc. The method of the present invention includes the following steps: material preparation, heating, blank prefabrication, pre-forging, closed-die forging, quenched-tempered heat treatment using waste heat, finish machining, flaw detection, etc. With the closed-die forging technology, the near-net-shape molding of the coupler knuckle can be achieved. The energy and the material are saved. The contour shape and the size do not need to be machined. The use ratio of the material can reach more than 92%. Moreover, during the entire molding, the workpiece is in the three-dimensionally stressed state all the time. The product has a dense texture, a high toughness, a good fatigue resistance, and a long lifetime.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the national phase of International Application No. PCT/CN2017/080671, filed on Apr. 14, 2017, which is based upon and claims priority to Chinese Patent Application No. 201610829867.7, filed on Sep. 10, 2016, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the technical field of plastic molding of complex parts, particularly to a method of near-net-shape forged molding of a coupler knuckle of a railway vehicle.

BACKGROUND

The railway vehicle coupler is the key part which is connected between the locomotive and the vehicle, and between vehicles. Moreover, the main part of the coupler portion is the coupler knuckle. Thus, the coupler knuckle is the key traction part of the railway vehicle. The performance of the coupler knuckle has a lot of things to do with the operating safety and reliability railway train. As the railway transportation of China is developing towards the direction of high speed and heavy load continuously, the longitudinal impact of the train increases drastically. The frictional wear of the contact surface of the coupler knuckle is severe. It is therefore more and more difficult for the performance of coupler knuckle to satisfy the requirement of modern railway transportation. Thus, the safety and benefit of the railway transportation are affected seriously. Currently, the manufacturing of coupler knuckle mainly is cast molding. During cast molding, organization defects such as air pore, slag inclusion, cavity shrinkage, loosening, and so on, are formed in the coupler knuckle. Under the effect of alternating stress, these defects cause cracks, leading to breakage. In practice and usage, the above phenomena occur frequently, causing huge loss. The operating safety of the railway vehicle is threatened seriously. Thus, forged coupler knuckle has become the preferred coupler knuckle for the high-speed train and heavy-loaded vehicle.

Since the cross-section of the coupler knuckle part changes significantly, the shape is complex, and the molding is difficult. Moreover, there are thin ribs that are not easy to forge. The difficulty of forging is high. Thus, very few manufacturers can achieve the forged molding.

Currently, the manufacturing method and process of forged coupler knuckle are complex. Multiple times of heating, die forging, and side cutting is necessary. Moreover, the blank after forged molding is significantly different from the finished product in terms of the shape and the size. It is necessary to rely on machining to process the coupler knuckle product into a certain shape and size. The energy and material are wasted. The manufacturing cost is high.

SUMMARY

The purpose of the present invention is to solve the problems that manufacturing forged coupler knuckles is difficult, and the process is complex, etc. A method of near-net-shape forged molding a coupler knuckle of a railway vehicle is proposed. With the manufacturing method of the present invention, the forged coupler knuckle blank with a high precision can be manufactured by the simplest processing method. The near-net-shape, rapidly, precise plastic molding of the forged coupler knuckle blank can be achieved.

Technical solutions of the present invention are as below:

A method of near-net-shape forged molding of the coupler knuckle of the railway vehicle includes the following steps:

a. material preparation: based on the product model, a certain length of steel rod of the corresponding mode is cut out with a band-sawing machine;

b. heating: the rough is heated to 1150° C.±20° C. by a 1500 KW medium-frequency induction heating apparatus;

c. the heated rough is positioned in an 800-ton multi-directional forging apparatus to be forged in multiple directions, and the blank is prefabricated.

d. blank pre-forging: the closed-die forging is performed on the prefabricated blank in the pre-forging die on a 2000-ton multi-directional forging apparatus, such that the blank is pre-forged with a certain shape and a certain size;

e. near-net-shape forged molding: the pre-forged blank is positioned in the coupler knuckle dedicated multi-directional forging die on a 6000-ton multi-directional forging apparatus to be subject to the closed-die forging, such that the near-net-shape molding is achieved;

f. thermal treatment: the forged blank is subject to a quenched-tempered heat treatment using waste heat;

g. finish machining: a pinhole and so on of coupler knuckle is processed using a numerical control machining special machine;

h. flaw detection: the magnetic powder flaw detection is performed on the finished product.

In Step d, the shape and the size of the blank are achieved by the multi-directional forging apparatus and pre-forging blank-making die.

Furthermore, in Step e, in the vertical direction, forged coupler knuckle dedicated multi-directional forging apparatus has three oil cylinders in total, i.e., a main oil cylinder, an upper ejection oil cylinder, and a lower ejection oil cylinder. In the horizontal direction, there are four oil cylinders in total, i.e., a left and a right molding and locking oil cylinders, and two ejection oil cylinders.

Furthermore, in Step e, the multi-directional forged molding die is a forged coupler knuckle dedicated die. The die uses a mixing manner to split horizontally and vertically. The die is composed of four portions, i.e., an upper portion, a lower portion, a left portion, and a right portion. The left and right portions of the die are provided with a built-in movable module which is driven by a built-in oil cylinder, such that the molding of a pocket portion of the forged coupler knuckle is achieved.

Furthermore, in Step e, the left and right portions of the die are respectively driven by two oil cylinders of the multi-directional forging apparatus in the horizontal direction to lock.

Furthermore, in Step e, the lower portion of the die in the vertical direction is fixed. The upper portion of the die is driven by the main oil cylinder of the multi-directional forging apparatus, so as to extrude and mold the rough in the closed-die.

Furthermore, in Step e, after closed-die forged molding, the forged coupler knuckle workpiece is pushed out by four ejection oil cylinders, i.e., the upper, the lower, the left, and the right ejection oil cylinders.

The moving speed of the main oil cylinder is adjustable within 50-80 mm/s in a stepless manner. The reduction is automatically controlled by the multi-directional forging apparatus based on the molding state of the workpiece, such that the rate of deformation of the workpiece is kept substantially the same during the entire molding.

The advantages of the present invention are as below:

(1) The molding precision is high. The contour, the shape, and the size are realized by the near-net-shape molding without the machining process. Thus, the raw material is saved (the raw material is saved for more than 15%), and the machining workload is saved.

(2) Compared with the current forging method, the heating times and forging process are reduced. The energy is saved. The productivity is improved.

(3) With the multi-directional closed-die forging near-net-shape molding technology, during the plastic deformation, the workpiece is in the three-dimensionally stressed state all the time. The molded workpiece has a dense texture and reasonable distribution of meat streamline. The bearing strength is significantly improved. There is zero defect inside the workpiece. The safety and the reliability can be guaranteed.

(4) Since the process of forged molding is simple, the number of auxiliary apparatus is less. The yield of finished product is high. An intellectualized manufacturing can be easily achieved.

(5) Compared with other forging methods, the productivity is improved for more than four times, and the manufacturing cost is lowered for about 50%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the flowchart of the process of the present invention.

FIG. 2 is the schematic diagram of the shape of the prefabricated blank of the present invention;

FIG. 3 is the structural schematic diagram of the pre-forged part of the present invention;

FIG. 4 is the structural schematic diagram of the forging blank of the near-net-shape molding forging of the coupler knuckle of the present invention;

FIG. 5 is the structural schematic diagram of the finished product of the forged coupler knuckle of the present invention;

FIG. 6 is the structural schematic diagram of the near-net-shape molding closed-die forging die of the present invention.

DETAILED DESCRIPTION

Hereinafter, the present invention is further described with reference to specific embodiments and drawings.

As shown in FIGS. 1-6, the method of near-net-shape forged molding of the coupler knuckle of the railway vehicle of the present invention includes the following steps:

Step (a) material preparation: based on the product model, a certain length of steel rod of the corresponding mode is cut out with a band-sawing machine.

Step (b) heating: the rough is heated to 1150° C.±20° C. by a 1500 KW medium-frequency induction heating apparatus.

Step (c) blank prefabrication: the heated rough is positioned in an 800-ton multi-directional forging apparatus to be forged in multiple directions, such that the blank is prefabricated.

Step (d) blank pre-forging: the closed-die forging is performed on the prefabricated blank in the pre-forging die on a 2000-ton multi-directional forging apparatus, such that the blank is pre-forged with a certain shape and a certain size.

Step (e) near-net-shape forged molding: the pre-forged blank is positioned in the coupler knuckle dedicated multi-directional forging die on a 6000-ton multi-directional forging apparatus to be subject to the closed-die forging, such that the near-net-shape molding is achieved.

Step (f) thermal treatment: the forged blank is subject to a quenched-tempered heat treatment using waste heat.

Step (g) finish machining: a pinhole and so on of coupler knuckle is processed using a numerical control machining special machine.

Step (h) flaw detection: the magnetic powder flaw detection is performed on the finished product.

In the above Step (c), the blank is prefabricated on multi-directional forging apparatus. The die in the vertical direction and the die in the horizontal direction move in an interleaved manner. The heated rough is made into the prefabricated blank with certain height and thickness within the shortest time. Meanwhile, the oxide skin on the surface of the rough is removed.

In the above Step (d), the blank is prefabricated is positioned in the pre-forging die of the multi-directional forging apparatus. The pre-forging die is divided into four portions, i.e., upper, lower, left, and right portions. The two portions, i.e., upper and lower portions of the die are driven by the vertical oil cylinder of the multi-directional forging apparatus. The two portions, i.e., left and right portions of the die are driven by the horizontal oil cylinder of the multi-directional forging apparatus. The movement and moving distance of each portion of the die are controlled by a program. After each portion of the die is assembled, the moving stops. The prefabricated blank is pre-forged into certain shape and size.

In the above Step (e), the near-net-shape molding of coupler knuckle is achieved by multi-directional forging apparatus and multi-directional forging die. Multi-directional forging die uses a mixing manner to split horizontally and vertically. After the pre-forged blank is positioned in the multi-directional forging die, at first, two portions in the horizontal direction of the die, i.e., the left and the right portions are driven by the horizontal oil cylinder of the multi-directional forging apparatus and start to move. The pre-forged blank is extruded. After the left portion of the die and the right portion of the die are assembled, the die is locked. The upper portion of the die in the vertical direction is driven by the main oil cylinder to move downward rapidly. When the upper portion of the die is about to contact the blank, main oil cylinder slows down. The closed-die forging starts. The moving speed of the upper portion of the die is adjustable in a stepless manner and is controlled by the program. During the entire forging, the rate of deformation of the workpiece is kept substantially the same all the way. When the pressure of the main oil cylinder reaches the predetermined value, the entire forging process is over. The upper portion of the die rapidly returns. Meanwhile, the upper ejection oil cylinder moves such that the workpiece is maintained without moving upward together with the upper portion of the die. The left and right portions of the die split and return. Next, the lower portion of the die is driven by the lower ejection oil cylinder to move upward to push out the workpiece, the near-net-shape forged molding is completed.

In the above Step (e), the horizontal die of multi-directional forging die is provided with a built-in hydraulic cylinder and a movable module. During closed-die forging, when the upper portion of the die moves downward to reach a certain position, the built-in hydraulic cylinder is controlled by the program to start automatically to push the movable module, so as to achieve the partial molding of the pocket portion of the coupler knuckle workpiece. While the upper portion of the die is returning rapidly, the built-in hydraulic cylinder starts to return, so as to drive the movable module to return. After the movable module returns to original position, left and right portions of the die split and return.

In the above Step (f), after the workpiece is molded, a quenched-tempered heat treatment is performed using the waste heat. After the near-net-shape forged molding of the workpiece is completed, the temperature is measured using an automatic temperature measuring system. Next, the workpiece enters the soaking pit. Based on the comparison of the temperature measured by the automatic temperature measuring system and the quenching temperature, the soaking pit performs a heating-up treatment or a cooling-down treatment on the workpiece automatically. The time for the workpiece to stay in the soaking pit is monitored in real time and automatically controlled by an accompanying automatic temperature measuring system.

Hereinafter, a specific embodiment of the method of the present invention is provided. In this embodiment, based on the model of forged coupler knuckle, rod material with the diameter of Ø150 mm and the length of 405 mm is prepared. The rod material blank is heated at 1150° C.±20° C. The heated rough is delivered into 800-ton multi-directional forging apparatus by a mechanical arm. The rough is prefabricated. Meanwhile, the oxide skin on the surface of the blank is removed. FIG. 2 is the schematic diagram of the shape of the prefabricated blank. Next, the mechanical arm delivers the prefabricated blank into the pre-forging die. multi-directional forging apparatus processes the prefabricated blank into a pre-forged part with certain shape and size. FIG. 3 is the structural schematic diagram of the pre-forged part. Next, the pre-forged blank is turned into the near-net-shape molding multi-directional closed-die forging die shown in FIG. 6, so as to achieve the near-net-shape forged molding of the coupler knuckle. Using the waste heat after blank molding, the blank workpiece is subject to evenly-heating treatment. Next, quenched-tempered heat treatment is performed automatically. FIG. 4 is the structural schematic diagram of forged coupler knuckle blank part after quenched-tempered heat treatment. FIG. 5 is the structural schematic diagram of the finished product of the forged coupler knuckle after the machining and flaw detection.

Hereinbefore, embodiments of the present invention are described in detail with reference to the drawings. However, the present invention is not limited to the above embodiments. Within the range of knowledge of the ordinary person skilled in the art, variations without departing the spirit of the present invention should all fall within the scope of the present invention patent. 

1. A method of near-net-shape forged molding of a coupler knuckle of a railway vehicle, comprising the following steps: Step (a) material preparation; Step (b) heating: heating a rough at 1150° C.±20° C.; Step (c) blank prefabrication: positioning the heated rough on an 800-ton multi-directional forging apparatus for multi-directional forging to prefabricate the blank; Step (d) blank pre-forging: closed-die forging the prefabricated blank in a pre-forging die on a 2000-ton multi-directional forging apparatus; Step (e) near-net-shape forged molding: closed-die forging the pre-forged blank positioned in a multi-directional forging die on a 6000-ton multi-directional forging apparatus, so as to achieve near-net-shape molding; Step (f) thermal treatment: performing a quenched-tempered heat treatment on the forged blank using waste heat; Step (g) finish machining: processing a pinhole of the coupler knuckle using a numerical control machining machine; and Step (h) flaw detection: performing a magnetic powder flaw detection on the finished product.
 2. The method of near-net-shape forged molding of the coupler knuckle of the railway vehicle according to claim 1, wherein in the Step (c) performing the blank prefabrication on the multi-directional forging apparatus; moving a die in a vertical direction and a die in a horizontal direction in an interleaved manner; manufacturing the heated rough into a prefabricated blank with a certain height and a certain thickness while removing an oxide skin on a surface of the rough.
 3. The method of near-net-shape forged molding of the coupler knuckle of the railway vehicle according to claim 1, wherein in the Step (d) positioning the prefabricated blank in the pre-forging die of the multi-directional forging apparatus; dividing the pre-forging die into four portions including an upper portion, a lower portion, a left portion, and a right portion; driving the upper portion and the lower portion of the die by a vertical oil cylinder of the multi-directional forging apparatus; driving the left portion and the right portion of the die by a horizontal oil cylinder of the multi-directional forging apparatus; controlling a movement and a moving distance of each portion of the die by a program; after each portion of the die is assembled, stopping moving of each portion of the die; and pre-forging the prefabricated blank into a certain shape and a certain size.
 4. The method of near-net-shape forged molding of the coupler knuckle of the railway vehicle according to claim 1, wherein in the Step (e) achieving the near-net-shape molding of the coupler knuckle by the multi-directional forging apparatus and the multi-directional forging die; splitting the multi-directional forging die horizontally and vertically in a mixing manner; after the pre-forged blank is positioned in the multi-directional forging die, at first, driving the left portion and the right portion of the die in a horizontal direction to start to move by the horizontal oil cylinder of the multi-directional forging apparatus; extruding the pre-forged blank; after the left portion and the right portion of the die are assembled, locking the die; driving the upper portion of the die in the vertical direction to move downward rapidly by a main oil cylinder; when the upper portion of the die is about to contact the blank, slowing down the main oil cylinder, and starting the closed-die forging, wherein a moving speed of the upper portion of the die is adjustable in a stepless manner and is controlled by the program; during the entire forging, keeping a rate of deformation of the workpiece substantially the same all the way; when a pressure of the main oil cylinder reaches a predetermined value, finishing the entire forging process; returning the upper portion of the die rapidly while moving an upper ejection oil cylinder such that the workpiece is maintained without moving upward together with the upper portion of the die; splitting and returning the left portion and the right portion of the die; next, driving the lower portion of the die by a lower ejection oil cylinder to move upward to push out the workpiece; and completing the near-net-shape forged molding.
 5. The method of near-net-shape forged molding of the coupler knuckle of the railway vehicle according to claim 1, wherein in the Step (e) providing the horizontal die of the multi-directional forging die with a built-in hydraulic cylinder and movable module; during the closed-die forging, when the upper portion of the die moves downward to reach a certain position, controlling the built-in hydraulic cylinder by the program to start automatically to push the movable module, so as to achieve a partial molding of a pocket portion of the coupler knuckle workpiece; while the upper portion of the die is returning rapidly, starting the built-in hydraulic cylinder to return, so as to drive the movable module to return; and after the movable module returns to an original position, splitting and returning the left portion and the right portion of the die.
 6. The method of near-net-shape forged molding of the coupler knuckle of the railway vehicle according to claim 1, wherein in the Step (f) after the workpiece is molded, performing a quenched-tempered heat treatment using the waste heat; after the near-net-shape forged molding of the workpiece is completed, measuring a temperature using an automatic temperature measuring system; next, entering the workpiece into a soaking pit; based on the comparison of the temperature measured by the automatic temperature measuring system and the quenching temperature, performing a heating-up treatment or a cooling-down treatment by the soaking pit on the workpiece automatically; and monitoring and automatically controlling a time for the workpiece to stay in the soaking pit in real time by an accompanying automatic temperature measuring system. 